In clamping devices of the aforesaid type, the situation arises that the workpiece, on being clamped, may be raised somewhat from the work table due to the play of the jaws in their guides and/or may lose its intended position on the work table. To solve this problem, the known clamping devices of the aforementioned type have to resort to relatively expensive constructional and structural means, resulting in the devices becoming complicated, bulky and correspondingly costly. Their maintenance must also fulfill many special requirements.
In cold sawing machines, particularly in power hacksaws, it is not previously known to use clamping devices of the kind referred to herein. This has, however, the drawback that in, for example, cutting lengths from bar stock the raising of the workpiece from the worktable during clamping leads to the cutting face being inclined from the desired plane. This runs counter to the continually increasing endeavors to saw off sections which need no reworking before further processing.
Particularly undesirable consequences arise, however, when the cold saw is provided with a feed device in the form of feed jaws arranged in series with the clamping jaws in the feed direction of the material to be sawn, which feeding jaws grip, e.g. rod-shaped material during the sawing process, feed it forward after the sawing process and after the opening of the clamping jaws, then release it at the beginning of the sawing process and after an adjustable return stroke, grip the material again. Namely, in this case the workpiece has no opportunity to fall back onto the work table on opening of the clamping jaws. Rather it is raised somewhat higher with each clamping step and therefore wanders higher step by step between the clamping jaws.